The lead acid battery using lead dioxide as the positive electrode active material and lead as the negative electrode active material, and also using sulfuric acid aqueous solution as the electrolyte solution is widely used in the industry since it is cheaper compared to other secondary battery and also since it is suitable for large current discharge. Thus, the importance thereof is not lost even though the high capacity secondary battery such as lithium ion secondary battery or so is popular today, and the study to improve the ability of the lead acid battery is carried out actively.
Recently, there are reports of the technique using activated carbons, in regards with the improvement of the large current discharge characteristic in short period of time, which is the advantage of the lead acid battery and the improvement of cycle characteristics having the large depth of discharge which is the disadvantage of the lead acid battery.
For example, the patent document 1 describes the lead acid battery using the negative electrode having the lead alloy porous body filled with the negative electrode in which 1 to 5 parts by weight of the activated carbon is added with respect to the negative electrode active material. Patent document 1 describes that this lead acid battery can hold high voltage of after 0.5 seconds at −15° C.
Patent document 2 describes the lead acid battery electrode formed with the active material layer comprising the activated carbons, the binder, and the conductive agent on the surface of the lead active material layer as the electrode active material; and Patent document 2 also describes the lead acid battery provided therewith. In Patent document 2, the active material layer comprising the activated carbons, the binder, and the conductive agent are formed by pulverizing the dry kneaded mixture by a cutter mixer, then adhering the obtained powder on the lead active material layer followed by applying the pressure; or it may be formed by mixing the active material, the binder solution, and the conductive agent, then coating the obtained active material layer forming composition on the lead active material layer. Further, Patent document 2 describes that the lead acid battery provided with this lead acid battery electrode exhibit higher power compared to that of conventional lead acid battery.
Patent document 3 describes the lead acid battery negative electrode placed by coating the paste which includes 13% of the lead active material to the one side across the grid shape current collector, and coating the paste which comprises the activated carbon, carbon black, carboxymethylcellulose on the other side across the grid shape current collector. Patent document 3, also describes the lead acid battery provided with said lead acid battery negative electrode. According to Patent document 3, it has good cycle characteristics which simulated the typical charge-discharge cycle in connection with the 42V mild hybrid electric automobile battery.    Patent document 1: JP-A-2003-51306    Patent document 2: JP-A-2007-12596 (corresponding US Patent application Publication No. 2006/269801)    Patent document 3: JP-A-2007-506230 (corresponding US Patent application Publication No. 2007/104981)